The basic aim of the project is to develop in small animals, models for the study of these human diseases which have a major impact on public health. The effort has been concentrated into four areas, models of immunodeficiency in mice and rats, a model for the study of rheumatoid arthritis in the rat, a model of Insulin Independent Diabetes Mellitus (IIDM) in the rat, and rat models for the study of chemical addiction. 1. Immunodeficient Mice: It has been shown that by appropriate treatment, the spleen cells of these mice become reconstituted with human lymphocytes. 2. Rheumatoid Arthritis in Rats: This model has established the interrelationship between the immune and nervous system contributing to this disease. 3. IDDM models in Rats: The model exhibits nearly all of the symptoms found in human to include vision, nervous, kidney, and other soft tissue involvement. 4. Chemical Addiction in Rats: Addiction and tolerance to various chemicals have a genetic basis in that they respond to selective breeding.